1. Field of the Invention
The present invention relates to a hybrid vehicle in which the engine drives a generator so as to generate the electric power for a driving motor and the output of the engine drives an electrical appliance such as an air conditioning system. More particularly, the present invention relates to a control method for an electrical appliance such as an air conditioning system especially at the time of starting and stopping the air conditioning system.
2. Description of the Related Art
An electric vehicle provided with an engine as well as a driving motor, namely, a hybrid vehicle is well known. For example, in a series hybrid vehicle, a generator is driven by the engine, and the motor is driven by the output of the generator. The motor is also driven by the discharge output of a battery mounted on the vehicle. The battery is charged by the output of the generator as well as by external power and regenerated power. This type of a vehicle is therefore advantageous in that a reduction in the size of the battery mounted thereon, as well as the frequency charging the battery by external power, is possible.
It is favorable from the point of view of comfortable driving conditions to mount an air conditioning system on a vehicle, such as an electric vehicle. In order to mount an air conditioning system on a vehicle, it is necessary to somehow produce power for driving the system on the vehicle. In the case of an electric vehicle, it is possible to utilize the output of the generator and the discharge power of the battery as the driving power for the air conditioning system. This method, however, is disadvantageous from the point of view of cost, because since the air conditioning system is driven by electric power, a motor or the like for driving a compressor of the air conditioning system is necessary. In contrast, as a method which is advantageous from the point of view of cost, there is a method of diverting an air conditioning system of a vehicle driven only by an engine, i.e., connecting the output shaft of the engine to the compressor of the air conditioning system so as to drive the compressor by the mechanical output of the engine.
In such a method of driving the compressor by the output of the engine, however, the load of the engine rapidly increases at the time of turning on the air conditioning system. This rapidly reduces the revolution speed of the engine and, in a worst case, stops the engine. In order to prevent the engine from stopping in this way, it is possible to increase the output of the engine by the equivalent to the consumption of the air conditioning system when the air conditioning system is turned on. However, the rapid increase in the output of the engine leads to an increase in the harmful exhaust gas component emitted from the engine. This is contrary to the intended purpose of an electric vehicle, that is, to prevent environmental pollution. In addition, in the case of a hybrid electric vehicle in which the engine is driven with high efficiency with a wide open throttle (WOT) so as to obtain good emission and the fuel consumption at the time of ordinary driving, a rapid increase in the output of the engine deviates from the output line of the engine with WOT. As a result, the emission and fuel consumption increase, thereby detracting from the merits of a hybrid vehicle brought about by operating with WOT.